Dynamically optimizing read performance by adjusting servo-based head location

ABSTRACT

In one embodiment, a method includes determining a reading performance based on one or more metrics, adjusting a commanded lateral reading location of a head relative to a medium, determining the reading performance after the adjusting, comparing the reading performance after the adjusting relative to the reading performance before the adjusting for determining whether the reading performance has improved, and selecting a commanded lateral reading location based on the comparing. In another embodiment, a controller is configured to perform the foregoing method. In yet another embodiment, a computer program product includes a computer readable storage medium having program instructions embodied therewith, the program instructions readable and/or executable by a controller configured to perform the foregoing method.

BACKGROUND

The present invention relates to data storage systems, and moreparticularly, this invention relates to optimizing dynamic tape trackread performance by comparing read performances of different headpositions and selecting a head position having higher relativeperformance than other locations.

In magnetic storage systems, magnetic transducers read data from andwrite data onto magnetic recording media. Data is written on themagnetic recording media by moving a magnetic recording transducer to aposition over the media where the data is to be stored. The magneticrecording transducer then generates a magnetic field, which encodes thedata into the magnetic media. Data is read from the media by similarlypositioning the magnetic read transducer and then sensing the magneticfield of the magnetic media. Read and write operations may beindependently synchronized with the movement of the media to ensure thatthe data can be read from and written to the desired location on themedia.

An important and continuing goal in the data storage industry is that ofincreasing the density of data stored on a medium. For tape storagesystems, that goal has led to increasing the track and linear bitdensity on recording tape, and decreasing the thickness of the magnetictape medium. However, the development of small footprint, higherperformance tape drive systems has created various problems in thedesign of a tape head assembly for use in such systems.

In a tape drive system, the drive moves the magnetic tape over thesurface of the tape head at high speed. Usually the tape head isdesigned to minimize the spacing between the head and the tape. Thespacing between the magnetic head and the magnetic tape is crucial andso goals in these systems are to have the recording gaps of thetransducers, which are the source of the magnetic recording flux in nearcontact with the tape to effect writing sharp transitions, and to havethe read elements in near contact with the tape to provide effectivecoupling of the magnetic field from the tape to the read elements.

BRIEF SUMMARY

In one embodiment, a method includes determining a reading performancebased on one or more metrics, adjusting a commanded lateral readinglocation of a head relative to a medium, determining the readingperformance after the adjusting, comparing the reading performance afterthe adjusting relative to the reading performance before the adjustingfor determining whether the reading performance has improved, andselecting a commanded lateral reading location based on the comparing.

In another embodiment, a controller is configured to perform theforegoing method.

In yet another embodiment, a computer program product includes acomputer readable storage medium having program instructions embodiedtherewith, the program instructions readable and/or executable by acontroller configured to perform the foregoing method.

Any of these embodiments may be implemented in a magnetic data storagesystem such as a tape drive system, which may include a magnetic head, adrive mechanism for passing a magnetic medium (e.g., recording tape)over the magnetic head, and a controller electrically coupled to themagnetic head.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a schematic diagram of a simplified tape drive systemaccording to one embodiment.

FIG. 1B is a schematic diagram of a tape cartridge according to oneembodiment.

FIG. 2 illustrates a side view of a flat-lapped, bi-directional;two-module magnetic tape head according to one embodiment.

FIG. 2A is a tape bearing surface view taken from Line 2A of FIG. 2.

FIG. 2B is a detailed view taken from Circle 2B of FIG. 2A.

FIG. 2C is a detailed view of a partial tape bearing surface of a pairof modules.

FIG. 3 is a partial tape bearing surface view of a magnetic head havinga write-read-write configuration.

FIG. 4 is a partial tape bearing surface view of a magnetic head havinga read-write-read configuration.

FIG. 5 is a side view of a magnetic tape head with three modulesaccording to one embodiment where the modules all generally lie alongabout parallel planes.

FIG. 6 is a side view of a magnetic tape head with three modules in atangent (angled) configuration.

FIG. 7 is a side view of a magnetic tape head with three modules in anoverwrap configuration.

FIG. 8 is a flow diagram of a method, according to one embodiment.

FIG. 9 is a flow diagram of a method, according to one embodiment.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several preferred embodiments ofmagnetic storage systems, as well as operation and/or component partsthereof.

In one general embodiment, a method includes determining a readingperformance based on one or more metrics, adjusting a commanded lateralreading location of a head relative to a medium, determining the readingperformance after the adjusting, comparing the reading performance afterthe adjusting relative to the reading performance before the adjustingfor determining whether the reading performance has improved, andselecting a commanded lateral reading location based on the comparing.

In another general embodiment, a controller is configured to perform theforegoing method.

In yet another general embodiment, a computer program product includes acomputer readable storage medium having program instructions embodiedtherewith, the program instructions readable and/or executable by acontroller configured to perform the foregoing method.

FIG. 1A illustrates a simplified tape drive 100 of a tape-based datastorage system, which may be employed in the context of the presentinvention. While one specific implementation of a tape drive is shown inFIG. 1A, it should be noted that the embodiments described herein may beimplemented in the context of any type of tape drive system.

As shown, a tape supply cartridge 120 and a take-up reel 121 areprovided to support a tape 122. One or more of the reels may form partof a removable cartridge and are not necessarily part of the system 100.The tape drive, such as that illustrated in FIG. 1A, may further includedrive motor(s) to drive the tape supply cartridge 120 and the take-upreel 121 to move the tape 122 over a tape head 126 of any type. Suchhead may include an array of readers, writers, or both.

Guides 125 guide the tape 122 across the tape head 126. Such tape head126 is in turn coupled to a controller 128 via a cable 130. Thecontroller 128, may be or include a processor and/or any logic forcontrolling any subsystem of the drive 100. For example, the controller128 typically controls head functions such as servo following, datawriting, data reading, etc. The controller 128 may include at least oneservo channel and at least one data channel, each of which include dataflow processing logic configured to process and/or store information tobe written to and/or read from the tape 122. The controller 128 mayoperate under logic known in the art, as well as any logic disclosedherein, and thus may be considered as a processor for any of thedescriptions of tape drives included herein, in various embodiments. Thecontroller 128 may be coupled to a memory 136 of any known type, whichmay store instructions executable by the controller 128. Moreover, thecontroller 128 may be configured and/or programmable to perform orcontrol some or all of the methodology presented herein. Thus, thecontroller 128 may be considered to be configured to perform variousoperations by way of logic programmed into one or more chips, modules,and/or blocks; software, firmware, and/or other instructions beingavailable to one or more processors; etc., and combinations thereof.

The cable 130 may include read/write circuits to transmit data to thehead 126 to be recorded on the tape 122 and to receive data read by thehead 126 from the tape 122. An actuator 132 controls position of thehead 126 relative to the tape 122.

An interface 134 may also be provided for communication between the tapedrive 100 and a host (integral or external) to send and receive the dataand for controlling the operation of the tape drive 100 andcommunicating the status of the tape drive 100 to the host, all as willbe understood by those of skill in the art.

FIG. 1B illustrates an exemplary tape cartridge 150 according to oneembodiment. Such tape cartridge 150 may be used with a system such asthat shown in FIG. 1A. As shown, the tape cartridge 150 includes ahousing 152, a tape 122 in the housing 152, and a nonvolatile memory 156coupled to the housing 152. In some approaches, the nonvolatile memory156 may be embedded inside the housing 152, as shown in FIG. 1B. In moreapproaches, the nonvolatile memory 156 may be attached to the inside oroutside of the housing 152 without modification of the housing 152. Forexample, the nonvolatile memory may be embedded in a self-adhesive label154. In one preferred embodiment, the nonvolatile memory 156 may be aFlash memory device, ROM device, etc., embedded into or coupled to theinside or outside of the tape cartridge 150. The nonvolatile memory isaccessible by the tape drive and the tape operating software (the driversoftware), and/or other device.

By way of example, FIG. 2 illustrates a side view of a flat-lapped,bi-directional, two-module magnetic tape head 200 which may beimplemented in the context of the present invention. As shown, the headincludes a pair of bases 202, each equipped with a module 204, and fixedat a small angle α with respect to each other. The bases may be“U-beams” that are adhesively coupled together. Each module 204 includesa substrate 204A and a closure 204B with a thin film portion, commonlyreferred to as a “gap” in which the readers and/or writers 206 areformed. In use, a tape 208 is moved over the modules 204 along a media(tape) bearing surface 209 in the manner shown for reading and writingdata on the tape 208 using the readers and writers. The wrap angle θ ofthe tape 208 at edges going onto and exiting the flat media supportsurfaces 209 are usually between about 0.1 degree and about 3 degrees.

The substrates 204A are typically constructed of a wear resistantmaterial, such as a ceramic. The closures 204B made of the same orsimilar ceramic as the substrates 204A.

The readers and writers may be arranged in a piggyback or mergedconfiguration. An illustrative piggybacked configuration comprises a(magnetically inductive) writer transducer on top of (or below) a(magnetically shielded) reader transducer (e.g., a magnetoresistivereader, etc.), wherein the poles of the writer and the shields of thereader are generally separated. An illustrative merged configurationcomprises one reader shield in the same physical layer as one writerpole (hence, “merged”). The readers and writers may also be arranged inan interleaved configuration. Alternatively, each array of channels maybe readers or writers only. Any of these arrays may contain one or moreservo track readers for reading servo data on the medium.

FIG. 2A illustrates the tape bearing surface 209 of one of the modules204 taken from Line 2A of FIG. 2. A representative tape 208 is shown indashed lines. The module 204 is preferably long enough to be able tosupport the tape as the head steps between data bands.

In this example, the tape 208 includes 4 to 22 data bands, e.g., with 16data bands and 17 servo tracks 210, as shown in FIG. 2A on a one-halfinch wide tape 208. The data bands are defined between servo tracks 210.Each data band may include a number of data tracks, for example 1024data tracks (not shown). During read/write operations, the readersand/or writers 206 are positioned to specific track positions within oneof the data bands. Outer readers, sometimes called servo readers, readthe servo tracks 210. The servo signals are in turn used to keep thereaders and/or writers 206 aligned with a particular set of tracksduring the read/write operations.

FIG. 2B depicts a plurality of readers and/or writers 206 formed in agap 218 on the module 204 in Circle 2B of FIG. 2A. As shown, the arrayof readers and writers 206 includes, for example, 16 writers 214, 16readers 216 and two servo readers 212, though the number of elements mayvary. Illustrative embodiments include 8, 16, 32, 40, and 64 activereaders and/or writers 206 per array, and alternatively interleaveddesigns having odd numbers of reader or writers such as 17, 25, 33, etc.An illustrative embodiment includes 32 readers per array and/or 32writers per array, here the actual number of transducer elements couldbe greater, e.g., 33, 34, etc. This allows the tape to travel moreslowly, thereby reducing speed-induced tracking and mechanicaldifficulties and/or execute fewer “wraps” to fill or read the tape.While the readers and writers may be arranged in a piggybackconfiguration as shown in FIG. 2B, the readers 216 and writers 214 mayalso be arranged in an interleaved configuration. Alternatively, eacharray of readers and/or writers 206 may be readers or writers only, andthe arrays may contain one or more servo readers 212. As noted byconsidering FIGS. 2 and 2A-B together, each module 204 may include acomplementary set of readers and/or writers 206 for such things asbi-directional reading and writing, read-while-write capability,backward compatibility, etc.

FIG. 2C shows a partial tape bearing surface view of complimentarymodules of a magnetic tape head 200 according to one embodiment. In thisembodiment, each module has a plurality of read/write (R/W) pairs in apiggyback configuration formed on a common substrate 204A and anoptional electrically insulative layer 236. The writers, exemplified bythe write transducer 214 and the readers, exemplified by the readtransducer 216, are aligned parallel to an intended direction of travelof a tape medium thereacross to form an R/W pair, exemplified by the R/Wpair 222. Note that the intended direction of tape travel is sometimesreferred to herein as the direction of tape travel, and such terms maybe used interchangeable. Such direction of tape travel may be inferredfrom the design of the system, e.g., by examining the guides; observingthe actual direction of tape travel relative to the reference point;etc. Moreover, in a system operable for bi-direction reading and/orwriting, the direction of tape travel in both directions is typicallyparallel and thus both directions may be considered equivalent to eachother.

Several R/W pairs 222 may be present, such as 8, 16, 32 pairs, etc. TheR/W pairs 222 as shown are linearly aligned in a direction generallyperpendicular to a direction of tape travel thereacross. However, thepairs may also be aligned diagonally, etc. Servo readers 212 arepositioned on the outside of the array of R/W pairs, the function ofwhich is well known.

Generally, the magnetic tape medium moves in either a forward or reversedirection as indicated by arrow 220. The magnetic tape medium and headassembly 200 operate in a transducing relationship in the mannerwell-known in the art. The piggybacked MR head assembly 200 includes twothin-film modules 224 and 226 of generally identical construction.

Modules 224 and 226 are joined together with a space present betweenclosures 204B thereof (partially shown) to form a single physical unitto provide read-while-write capability by activating the writer of theleading module and reader of the trailing module aligned with the writerof the leading module parallel to the direction of tape travel relativethereto. When a module 224, 226 of a piggyback head 200 is constructed,layers are formed in the gap 218 created above an electricallyconductive substrate 204A (partially shown), e.g., of AlTiC, ingenerally the following order for the R/W pairs 222: an insulating layer236, a first shield 232 typically of an iron alloy such as NiFe (−), CZTor Al—Fe—Si (Sendust), a sensor 234 for sensing a data track on amagnetic medium, a second shield 238 typically of a nickel-iron alloy(e.g., ˜80/20 at % NiFe, also known as permalloy), first and secondwriter pole tips 228, 230, and a coil (not shown). The sensor may be ofany known type, including those based on MR, GMR, AMR, tunnelingmagnetoresistance (TMR), etc.

The first and second writer poles 228, 230 may be fabricated from highmagnetic moment materials such as ˜45/55 NiFe. Note that these materialsare provided by way of example only, and other materials may be used.Additional layers such as insulation between the shields and/or poletips and an insulation layer surrounding the sensor may be present.Illustrative materials for the insulation include alumina and otheroxides, insulative polymers, etc.

The configuration of the tape head 126 according to one embodimentincludes multiple modules, preferably three or more. In awrite-read-write (W-R-W) head, outer modules for writing flank one ormore inner modules for reading. Referring to FIG. 3, depicting a W-R-Wconfiguration, the outer modules 252, 256 each include one or morearrays of writers 260. The inner module 254 of FIG. 3 includes one ormore arrays of readers 258 in a similar configuration. Variations of amulti-module head include a R-W-R head (FIG. 4), a R-R-W head, a W-W-Rhead, etc. In yet other variations, one or more of the modules may haveread/write pairs of transducers. Moreover, more than three modules maybe present. In further approaches, two outer modules may flank two ormore inner modules, e.g., in a W-R-R-W, a R-W-W-R arrangement, etc. Forsimplicity, a W-R-W head is used primarily herein to exemplifyembodiments of the present invention. One skilled in the art apprisedwith the teachings herein will appreciate how permutations of thepresent invention would apply to configurations other than a W-R-Wconfiguration.

FIG. 5 illustrates a magnetic head 126 according to one embodiment ofthe present invention that includes first, second and third modules 302,304, 306 each having a tape bearing surface 308, 310, 312 respectively,which may be flat, contoured, etc. Note that while the term “tapebearing surface” appears to imply that the surface facing the tape 315is in physical contact with the tape bearing surface, this is notnecessarily the case. Rather, only a portion of the tape may be incontact with the tape bearing surface, constantly or intermittently,with other portions of the tape riding (or “flying”) above the tapebearing surface on a layer of air, sometimes referred to as an “airbearing”. The first module 302 will be referred to as the “leading”module as it is the first module encountered by the tape in a threemodule design for tape moving in the indicated direction. The thirdmodule 306 will be referred to as the “trailing” module. The trailingmodule follows the middle module and is the last module seen by the tapein a three module design. The leading and trailing modules 302, 306 arereferred to collectively as outer modules. Also note that the outermodules 302, 306 will alternate as leading modules, depending on thedirection of travel of the tape 315.

In one embodiment, the tape bearing surfaces 308, 310, 312 of the first,second and third modules 302, 304, 306 lie on about parallel planes(which is meant to include parallel and nearly parallel planes, e.g.,between parallel and tangential as in FIG. 6), and the tape bearingsurface 310 of the second module 304 is above the tape bearing surfaces308, 312 of the first and third modules 302, 306. As described below,this has the effect of creating the desired wrap angle α₂ of the taperelative to the tape bearing surface 310 of the second module 304.

Where the tape bearing surfaces 308, 310, 312 lie along parallel ornearly parallel yet offset planes, intuitively, the tape should peel offof the tape bearing surface 308 of the leading module 302. However, thevacuum created by the skiving edge 318 of the leading module 302 hasbeen found by experimentation to be sufficient to keep the tape adheredto the tape bearing surface 308 of the leading module 302. The trailingedge 320 of the leading module 302 (the end from which the tape leavesthe leading module 302) is the approximate reference point which definesthe wrap angle α₂ over the tape bearing surface 310 of the second module304. The tape stays in close proximity to the tape bearing surface untilclose to the trailing edge 320 of the leading module 302. Accordingly,read and/or write elements 322 may be located near the trailing edges ofthe outer modules 302, 306. These embodiments are particularly adaptedfor write-read-write applications.

A benefit of this and other embodiments described herein is that,because the outer modules 302, 306 are fixed at a determined offset fromthe second module 304, the inner wrap angle α₂ is fixed when the modules302, 304, 306 are coupled together or are otherwise fixed into a head.The inner wrap angle α₂ is approximately tan⁻¹(δ/W) where δ is theheight difference between the planes of the tape bearing surfaces 308,310 and W is the width between the opposing ends of the tape bearingsurfaces 308, 310. An illustrative inner wrap angle α₂ is in a range ofabout 0.3° to about 1.1°, though can be any angle required by thedesign.

Beneficially, the inner wrap angle α₂ on the side of the module 304receiving the tape (leading edge) will be larger than the inner wrapangle α₃ on the trailing edge, as the tape 315 rides above the trailingmodule 306. This difference is generally beneficial as a smaller α₃tends to oppose what has heretofore been a steeper exiting effectivewrap angle.

Note that the tape bearing surfaces 308, 312 of the outer modules 302,306 are positioned to achieve a negative wrap angle at the trailing edge320 of the leading module 302. This is generally beneficial in helpingto reduce friction due to contact with the trailing edge 320, providedthat proper consideration is given to the location of the crowbar regionthat forms in the tape where it peels off the head. This negative wrapangle also reduces flutter and scrubbing damage to the elements on theleading module 302. Further, at the trailing module 306, the tape 315flies over the tape bearing surface 312 so there is virtually no wear onthe elements when tape is moving in this direction. Particularly, thetape 315 entrains air and so will not significantly ride on the tapebearing surface 312 of the third module 306 (some contact may occur).This is permissible, because the leading module 302 is writing while thetrailing module 306 is idle.

Writing and reading functions are performed by different modules at anygiven time. In one embodiment, the second module 304 includes aplurality of data and optional servo readers 331 and no writers. Thefirst and third modules 302, 306 include a plurality of writers 322 andno data readers, with the exception that the outer modules 302, 306 mayinclude optional servo readers. The servo readers may be used toposition the head during reading and/or writing operations. The servoreader(s) on each module are typically located towards the end of thearray of readers or writers.

By having only readers or side by side writers and servo readers in thegap between the substrate and closure, the gap length can besubstantially reduced. Typical heads have piggybacked readers andwriters, where the writer is formed above each reader. A typical gap is20-35 microns. However, irregularities on the tape may tend to droopinto the gap and create gap erosion. Thus, the smaller the gap is thebetter. The smaller gap enabled herein exhibits fewer wear relatedproblems.

In some embodiments, the second module 304 has a closure, while thefirst and third modules 302, 306 do not have a closure. Where there isno closure, preferably a hard coating is added to the module. Onepreferred coating is diamond-like carbon (DLC).

In the embodiment shown in FIG. 5, the first, second, and third modules302, 304, 306 each have a closure 332, 334, 336, which extends the tapebearing surface of the associated module, thereby effectivelypositioning the read/write elements away from the edge of the tapebearing surface. The closure 332 on the second module 304 can be aceramic closure of a type typically found on tape heads. The closures334, 336 of the first and third modules 302, 306, however, may beshorter than the closure 332 of the second module 304 as measuredparallel to a direction of tape travel over the respective module. Thisenables positioning the modules closer together. One way to produceshorter closures 334, 336 is to lap the standard ceramic closures of thesecond module 304 an additional amount. Another way is to plate ordeposit thin film closures above the elements during thin filmprocessing. For example, a thin film closure of a hard material such asSendust or nickel-iron alloy (e.g., 45/55) can be formed on the module.

With reduced-thickness ceramic or thin film closures 334, 336 or noclosures on the outer modules 302, 306, the write-to-read gap spacingcan be reduced to less than about 1 mm, e.g., about 0.75 mm, or 50% lessthan commonly-used LTO tape head spacing. The open space between themodules 302, 304, 306 can still be set to approximately 0.5 to 0.6 mm,which in some embodiments is ideal for stabilizing tape motion over thesecond module 304.

Depending on tape tension and stiffness, it may be desirable to anglethe tape bearing surfaces of the outer modules relative to the tapebearing surface of the second module. FIG. 6 illustrates an embodimentwhere the modules 302, 304, 306 are in a tangent or nearly tangent(angled) configuration. Particularly, the tape bearing surfaces of theouter modules 302, 306 are about parallel to the tape at the desiredwrap angle α₂ of the second module 304. In other words, the planes ofthe tape bearing surfaces 308, 312 of the outer modules 302, 306 areoriented at about the desired wrap angle α₂ of the tape 315 relative tothe second module 304. The tape will also pop off of the trailing module306 in this embodiment, thereby reducing wear on the elements in thetrailing module 306. These embodiments are particularly useful forwrite-read-write applications. Additional aspects of these embodimentsare similar to those given above.

Typically, the tape wrap angles may be set about midway between theembodiments shown in FIGS. 5 and 6.

FIG. 7 illustrates an embodiment where the modules 302, 304, 306 are inan overwrap configuration. Particularly, the tape bearing surfaces 308,312 of the outer modules 302, 306 are angled slightly more than the tape315 when set at the desired wrap angle α₂ relative to the second module304. In this embodiment, the tape does not pop off of the trailingmodule, allowing it to be used for writing or reading. Accordingly, theleading and middle modules can both perform reading and/or writingfunctions while the trailing module can read any just-written data.Thus, these embodiments are preferred for write-read-write,read-write-read, and write-write-read applications. In the latterembodiments, closures should be wider than the tape canopies forensuring read capability. The wider closures may require a widergap-to-gap separation. Therefore a preferred embodiment has awrite-read-write configuration, which may use shortened closures thatthus allow closer gap-to-gap separation.

Additional aspects of the embodiments shown in FIGS. 6 and 7 are similarin those given above.

A 32 channel version of a multi-module head 126 may use cables 350having leads on the same or smaller pitch as current 16 channelpiggyback LTO modules, or alternatively the connections on the modulemay be organ-keyboarded for a 50% reduction in cable span. Over-under,writing pair unshielded cables may be used for the writers, which mayhave integrated servo readers.

The outer wrap angles α₁ may be set in the drive, such as by guides ofany type known in the art, such as adjustable rollers, slides, etc. oralternatively by outriggers, which are integral to the head. Forexample, rollers having an offset axis may be used to set the wrapangles. The offset axis creates an orbital arc of rotation, allowingprecise alignment of the wrap angle α₁.

To assemble any of the embodiments described above, conventional u-beamassembly can be used. Accordingly, the mass of the resultant head may bemaintained or even reduced relative to heads of previous generations. Inother approaches, the modules may be constructed as a unitary body.Those skilled in the art, armed with the present teachings, willappreciate that other known methods of manufacturing such heads may beadapted for use in constructing such heads.

As described above, in a typical tape drive, the lateral position of ahead relative to the tape is servo-controlled. Due to shingling, orpartial overwriting of a previous track to leave a smaller resultantwritten track, the writer on a head is larger than the resultant trackwidth. With a writer width and the shingling track pitch known, alateral position may be calculated to guide/place a reader in the centerof the track initially during reading. The offset, or difference,between the writing location of the non-shingled track and the readinglocation of the shingled track can be calculated as (WTW−WTP)/2, whereWTW is the writer track width and WTP is the written track pitch.However, because data writers may not be precisely located with respectto the servo readers, the data may not be written in the ideal location.Therefore, when it is attempted to read these tracks, the reader may notbe ideally located in the center of the written track. Additionally,tracks and/or tape often experience temperature stress, stretching,shingling data loss, tape lateral expansion or contraction due toenvironmental changes, etc., the calculated center of a track may not bethe most optimal location for reading.

As tape drive capacity has increased over time, both the writer widthand track pitch have steadily decreased. Additionally, the reader widthhas not decreased at the same rate, and therefore the margins betweenthe edges of the reader and the edges of written track have decreased.Due to magnetic properties, the writer has a tendency to magneticallyalter regions that are slightly outside the writer width. This is knownas sidewriting. In the past, tracks were relatively large, andsidewriting comprised a smaller percentage of a written track width thanit now does on condensed tracks.

In the process of writing data to a second track, which is shingling afirst track, sidewriting has a tendency to erase part of the firsttrack. The resultant magnetic track width is undesirably different andsmaller than the track pitch. Additionally, in some embodiments, theresultant reader element may not have a magnetic width that is equal tothe physical reader width. The reader magnetic sensitivity may also benon-uniform such that it appears that the reader is not in the center ofthe track. This may lead to reading errors and non-optimal reads.

For the reasons explained above, determining the servo location forreading by simply calculating a position using the writer width andtrack pitch may lead to a reader which is not centered on the shingledtrack. When the reader is not centered, the reading performance isdegraded.

Embodiments described herein provide a method, computer program product,apparatus, etc. for continuously optimizing a location for a tape headduring reading, rather than just using a pre-programmed read location.

Various embodiments for centering readers in shingled tracks aredescribed below. Embodiments described herein utilize the internalreading performance of a drive to find an optimal servo location inorder to maximize reading performance while a drive is actively reading.

Now referring to FIG. 8, a flowchart of a method 800 is shown accordingto one embodiment. The method 800 may be performed in accordance withthe present invention in any of the environments depicted in FIGS. 1-9,among others, in various embodiments. Of course, more or less operationsthan those specifically described in FIG. 8 may be included in method800, as would be understood by one of skill in the art upon reading thepresent descriptions.

Each of the steps of the method 800 may be performed by any suitablecomponent of the operating environment. The processor, e.g., processingcircuit(s), chip(s), and/or module(s) implemented in hardware and/orsoftware, and preferably having at least one hardware component may beutilized in any device to perform one or more steps of the method 800.Illustrative processors include, but are not limited to, a centralprocessing unit (CPU), an application specific integrated circuit(ASIC), a field programmable gate array (FPGA), etc., combinationsthereof, or any other suitable computing device known in the art.

A drive in one approach may begin reading in a typical servo readinglocation, e.g. calculated using the writer width and shingled trackpitch (described above), etc.

In another approach, a more optimal tape location to begin reading atbefore initiating the read performance improvement described herein maybe determined by assessing data tracks not (or least) damaged, skewed,etc. by temperature stress, design modifications, stretching, shinglingdata loss, tape lateral expansion, etc. For example, in a 32 channeldrive, if the tape has laterally expanded due to high temperaturesand/or high humidity in the drive, the tracks on tape corresponding tothe outermost channels may be most expanded, etc., in which case thereader may be centered on and begin reading where the innermost channelsare now positioned.

In order to improve read performance, as illustrated in operation 802 ofFIG. 8, according to one approach a reading performance may bedetermined, based on one or more metrics, which may represent a measureof quality. The one or more metrics upon which the reading performancemay be based includes C1 error correction rates, C2 error correctionrates, soft errors, temporary errors, soft error rates, mean squareerror rates, and any other error characteristics and/or metrics known inthe art, as would become apparent to one skilled in the art upon readingthe present disclosure.

C1 error correction rates and C2 error correction rates typically referto an error rate based on the decoding of a read channel. Particularly,the C1 error rate, which is available per track, and applied first inECC, is the number of bytes corrected by the C1 code. C2 error rate,which is a single value, is representative of the correction required tocorrect any errors still remaining after the C1 is applied, and istypically output as the number of bytes corrected, this time across alltracks.

Yet another approach uses the C1 uncorrectable rate, also available pertrack, which describes the number of C1 entities that were notcorrected. The C1 entity is normally a “codeword” or “codeword object”.

Temporary soft errors typically occur when there is an error with thesignal a drive component is receiving and/or with the datum, etc.Temporary errors typically relate to drive errors, etc.

In further embodiments, the output from a maximum likelihood detectormay provide a per track measure of quality, e.g., mean square error(MSE). The detector in the data channel constantly monitors and attemptsto detect 1 or 0 by minimizing the MSE. This value may be available foreach detected bit, and in some approaches, the filtered (smoothed) MSEis available to observe as a measure of detection quality. It can bechecked at any time by code to determine a measure of quality. Note thatit is, by its nature, not a measure of detection errors.

In various embodiments, the measures of quality are all most easilyavailable after each dataset (DS) is read or written. The measurementmay be performed across multiple datasets 10-20 datasets) to determinethe trend of the parameters. Then an action may be taken after adetermination is made as to whether the quality is the same, better, orworse. Various approaches are not limited to the multi-DS trending, butrather respond at each DS. There may be some interaction between theread offset amount (size of step) and the frequency of change. In oneapproach, care is taken to keep the offsetting amount small and allowingthe read system to settle somewhat before a quality determination ismade. Parameters such as the offsetting amount and time to settle may bereadily determined by one skilled in the art upon reading the presentdisclosure.

When using C2 correction data, the reader may simply be shifted aroundattempting to minimize those corrections.

The per track measurements may allow a track profile to be established.In one exemplary approach, assume there is available 32 tracks of C1correction, C1 uncorrectables, and detector MSE at each DS read. Theseprovide the ability to observe, for example, if the lower numberedtracks are worse than the upper tracks, in which case a step directioncan be determined (e.g., offset reader towards higher tracks, hopefullyshifting the lower tracks to be more on track, and not degrading theupper tracks).

Aside from track profiling, the quality metric may include comparing thenumber of tracks that improved or degraded from a previous measurement,and generating a scoring in a manner known in the art.

It should also be mentioned that the per track values above (not the C2)are available during write, which can provide a good benchmark readingfor “best case” values for C1 corrections, C1 uncorrectable, and MSE.This may be valuable because, in various embodiments, the writingcondition is the best measure of current system capability because it isnot subject to off-track or other read degradations. That is, ifbenchmark values are captured during write, then these can be comparedto values attained on read providing good profiling information. Forexample, if a read track is dead for any reason, then the per trackmetrics would be poor for that track during write, and perhaps it can beeliminated from the profiling work described above.

In various embodiments, reading performance may be determined using atechnique known in the art, as would become apparent to one skilled inthe art upon reading the present disclosure. Additionally readingperformance may be determined using information from multiple readchannels configured to operate simultaneously. Furthermore, a readingperformance may be determined using information from a single channel.

Additionally, according to operation 804, the commanded lateral readinglocation, e.g. servo reading location, etc. of a head relative to amedium e.g., magnetic medium, optical medium, etc. is adjusted. Theadjustment may be initiated after a command is issued to the driveactuator. The adjustment of the commanded lateral reading location of ahead relative to a medium (as described above) may be adjusted by apredefined increment, e.g. a set shift allotment, “click” or “tick” etc.in a digital domain, while in the analog domain, the number of shifts isessentially infinite. The number of shifts (“clicks” or “ticks” etc.)allocated for each adjustment of the commanded lateral reading locationof a head relative to a medium may be one, two, three, n-shifts, etc.The predefined adjustment increment may be changed depending on theembodiment.

After the adjustment of operation 804 is performed, the readingperformance may be determined as noted in operation 806 of FIG. 8.Reading performance may be determined using any of the techniques usedin operation 802, and preferably the same technique, as will soon becomeapparent.

The reading performance of operation 806, taken after the adjustment ofoperation 804 may be compared to the reading performance before theadjusting for determining whether the reading performance has improved,or equivalently changed but not worsened, as noted in operation 808.Based on the comparison of operation 808, a commanded lateral readinglocation is selected as noted by operation 810. For example, if the newreading performance is better, the commanded lateral reading locationmay be set at the location after adjustment. Conversely, if the newreading performance is worse, the commanded lateral reading location maybe set at the location prior to adjustment. Moreover, the foregoingselecting may include several adjusting and comparing cycles, inmultiple directions, to obtain the desired commanded lateral readinglocation, as will be described in further detail below.

When the reading performance has improved after the adjusting, orequivalently change but not worsened, the commanded lateral readinglocation may be maintained. In another approach, the commanded lateralreading location may be adjusted in a same direction and a resultingreading performance is compared with a previous reading performance.When the reading performance has not improved after the adjusting, orequivalently not changed and/or worsened, the commanded lateral readinglocation may be maintained. In another approach, the commanded lateralreading location may be adjusted in a different e.g., opposite directionand a resulting reading performance is compared with a previous readingperformance. Further adjustments based on the approaches described abovewill be described below in a preferred embodiment of read performanceimprovement (see FIG. 9).

Now referring to FIG. 9, a flowchart of a method 900 is shown accordingto one embodiment. The method 900 may be performed in accordance withthe present invention in any of the environments depicted in FIGS. 1-8,among others, in various embodiments. Of course, more or less operationsthan those specifically described in FIG. 9 may be included in method900, as would be understood by one of skill in the art upon reading thepresent descriptions.

Each of the steps of the method 900 may be performed by any suitablecomponent of the operating environment. The processor, e.g., processingcircuit(s), chip(s), and/or module(s) implemented in hardware and/orsoftware, and preferably having at least one hardware component may beutilized in any device to perform one or more steps of the method 900.Illustrative processors include, but are not limited to, a centralprocessing unit (CPU), an application specific integrated circuit(ASIC), a field programmable gate array (FPGA), etc., combinationsthereof, or any other suitable computing device known in the art.

As noted in operation 902 of FIG. 9, a preferred embodiment may measurea reading performance by a C1 error correction rate, C2 error correctionrate, and/or some other metric. As described above with reference toFIG. 8, other metrics may include soft errors, temporary errors, and anyother errors or metric known in the art, as would become apparent to oneskilled in the art upon reading the present disclosure.

With reference now to operation 904, the commanded lateral readinglocation is shifted in a first directions. As described above, thecommanded lateral reading location shift may be adjusted by a predefinedincrement, e.g. a set shift allotment, “click” or “tick” etc. in adigital domain, while in the analog domain, the number of shifts isinfinite. The predefined adjustment increment may be changed dependingon the embodiment and/or user preference. In one approach, a shift incommanded lateral reading location results in an actuator moving thefirst direction the number by a distance corresponding to the predefinedadjustment increment.

Once the commanded lateral reading location has been shifted (seeoperation 904 of FIG. 9), the reading performance of the data may beagain measured by a C1 error correction rate, C2 error correction rate,or some other metric, as noted in operation 906.

Method 900 compares the reading performances of operations 902 and 906,as shown in comparator 908 of FIG. 9, to determine if the readingperformance at the new lateral servo location (906) has improved fromthe previous lateral servo location (902). In cases where the comparator908 determines that the reading performance at the new lateral servolocation (906) has improved from the previous lateral servo location(902) as denoted by the “YES” lead of comparator 908 of FIG. 9,operation 904 is again conducted, and the commanded lateral readinglocation is again shifted in a first direction. Additionally, when thecomparator 908 determines that the reading performance at the newlateral servo location (906) has not improved from the previous lateralservo location (902) as denoted by “NO” lead of comparator 908,operation 910 may be conducted, in which the commanded lateral readinglocation is shifted in a second direction opposite the first direction.

The shift allotment, number of clicks, number of ticks, etc. allocatedto a shift of the commanded lateral reading location in a secondopposite direction may be incrementally, numerically, periodically, etc.different than the shift allotment, number of clicks, number of ticksetc. allocated to a shift of the commanded lateral reading location in afirst direction. Likewise, the shift allotment, number of clicks, numberof ticks etc. allocated to a shift of the commanded lateral readinglocation in a second opposite direction may be incrementally,numerically, periodically, etc. equal to the shift allotment, number ofclicks, number of ticks etc. allocated to a shift of the commandedlateral reading location in a first direction.

Following the commanded lateral reading location shift in a seconddirection (operation 910), the reading performance of the data ismeasured by C1 error correction rate, C2 error correction rate, or someother metric as previously noted. Based on the determined readingperformance of operation 912, comparator 914 determines whether thereading performance at the new lateral servo location (910) has improvedfrom the previous lateral servo location (904).

In cases where the comparator 914 determines that the readingperformance at the new lateral servo location (910) has improved fromthe previous lateral servo location (904) as denoted by the “YES” leadof comparator 914, operation 910 is again performed, and the commandedlateral reading location is again shifted in a second oppositedirection. Additionally, when the comparator 914 determines that thereading performance at the new lateral servo location (910) has notimproved from the previous lateral servo location (904) as denoted by“NO” lead of comparator 914, the optimal commanded lateral readinglocation has been found as noted by operation 916. In some preferredembodiments, once the optimal commanded lateral reading location hasbeen found, as noted in operation 916, reading will continue at thefound location until operation 902 is again initiated, e.g., after someperiod, upon occurrence of a trigger event, etc.

According to various embodiments, the apparatus described herein isconfigured to perform the determining, comparing and adjustingperiodically. The periodic interval at which the apparatus is configuredto perform the determining, comparing and adjusting may vary dependingon the preferred embodiment. The periodic interval may be static orvariable. The periodic interval may be less than 1 second in someapproaches. In other approaches, longer periodic intervals are used.

In another approach, the determining, comparing and adjusting may beperformed immediately after the end of a previous determining, comparingor adjusting. For example, after it has been determined in operation 916that the optimal lateral servo location has been found in comparator914, operation 902 may be initiated immediately, or after reading hasoccurred at the optimal lateral servo position for any period of time.

In a further embodiment, the apparatus described herein is configured toperform the determining, comparing and adjusting upon occurrence of atrigger condition. A trigger condition may include e.g. logical inputs,user inputs, system temperature/stress flags, etc.

In yet a further embodiment, the apparatus described herein isconfigured to perform the determining, comparing and adjusting uponoccurrence of the end of a timer sequence.

In an even yet further embodiment, the apparatus described herein isconfigured to perform the determining, comparing and adjusting basedupon a combination of the foregoing. For example, the process may occurat some default period until a trigger condition occurs, upon which theperiodic interval is shortened.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Moreover, a system according to various embodiments may include aprocessor and logic integrated with and/or executable by the processor,the logic being configured to perform one or more of the process stepsrecited herein. By integrated with, what is meant is that the processorhas logic embedded therewith as hardware logic, such as an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA), etc. By executable by the processor, what is meant is that thelogic is hardware logic; software logic such as firmware, part of anoperating system, part of an application program; etc., or somecombination of hardware and software logic that is accessible by theprocessor and configured to cause the processor to perform somefunctionality upon execution by the processor. Software logic may bestored on local and/or remote memory of any memory type, as known in theart. Any processor known in the art may be used, such as a softwareprocessor module and/or a hardware processor such as an ASIC, a FPGA, acentral processing unit (CPU), an integrated circuit (IC), etc.

It will be clear that the various features of the foregoing systemsand/or methodologies may be combined in any way, creating a plurality ofcombinations from the descriptions presented above.

It will be further appreciated that embodiments of the present inventionmay be provided in the form of a service deployed on behalf of acustomer.

The inventive concepts disclosed herein have been presented by way ofexample to illustrate the myriad features thereof in a plurality ofillustrative scenarios, embodiments, and/or implementations. It shouldbe appreciated that the concepts generally disclosed are to beconsidered as modular, and may be implemented in any combination,permutation, or synthesis thereof. In addition, any modification,alteration, or equivalent of the presently disclosed features,functions, and concepts that would be appreciated by a person havingordinary skill in the art upon reading the instant descriptions shouldalso be considered within the scope of this disclosure.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of an embodiment of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A computer-implemented method, comprising:determining a reading performance of a head positioned at a commandedlateral reading location based on one or more metrics; adjusting alateral reading location of the head relative to a medium by moving thehead in a lateral direction away from the commanded lateral readinglocation to an adjusted lateral reading location; determining a readingperformance of the head after the adjusting; comparing the readingperformance after the adjusting to the reading performance before theadjusting for determining whether the reading performance has improved;and selecting an optimal lateral reading location based on thecomparing; wherein the one or more metrics comprise one or morebenchmark values captured during one or more write operations.
 2. Themethod of claim 1, in response to determining the reading performancehas improved after the adjusting, performing at least one of:maintaining the adjusted lateral reading location, and adjusting thelateral reading location of the head by moving the head away from theadjusted lateral reading location in the lateral direction and comparinga resulting reading performance with a previous reading performance. 3.The method of claim 1, comprising, in response to determining thereading performance has not improved after the adjusting, adjusting thelateral reading location of the head by moving the head away from thecommanded lateral reading location in a different lateral direction andcomparing a resulting reading performance with a previous readingperformance.
 4. The method of claim 1, wherein the determining, thecomparing and the adjusting are performed in response to detecting atrigger condition comprising one or more of a logical input, a userinput, and end of a timer sequence, a system humidity warning, and asystem temperature warning.
 5. The method of claim 1, wherein thedetermining, the adjusting and the comparing are performed continuouslywhile the head is actively engaged in a read operation.
 6. The method ofclaim 1, wherein the one or more metrics are selected from a groupconsisting of C1 error correction rate, and C2 error correction rate. 7.The method of claim 1, wherein the reading performance is determinedusing information from multiple read channels configured to operatesimultaneously, wherein when the reading performance has improved afterthe adjusting, at least one of: maintaining the adjusted lateral readinglocation, and adjusting the adjusted lateral reading location by movingthe head away from the adjusted lateral reading location in the lateraldirection and comparing a resulting reading performance with a previousreading performance, wherein when the reading performance has notimproved after the adjusting, at least one of: maintaining the adjustedlateral reading location, restoring the head to the commanded lateralreading location; and adjusting the adjusted lateral reading location bymoving the head away from the commanded lateral reading location in adifferent lateral direction and comparing a resulting readingperformance with a previous reading performance, and wherein the one ormore metrics are selected from a group consisting of C1 error correctionrate, C2 error correction rate, mean square error rate, and output froma maximum likelihood detector.
 8. An apparatus, comprising: a controllerand logic integrated with and/or executable by the controller to:determine a reading performance of a head positioned at a commandedlateral reading location based on one or more metrics; adjust a lateralreading location of the head relative to a medium by instructing thehead to move in a lateral direction away from the commanded lateralreading location in to an adjusted lateral reading location; determinethe reading performance of the head after the adjustment; compare thereading performance after adjustment to the reading performance beforeadjustment for determining whether the reading performance has improved;and select an optimal lateral reading location based on the comparing,wherein the one or more metrics comprise one or more benchmark valuescaptured during one or more write operations.
 9. An apparatus as recitedin claim 8, further comprising logic integrated with and/or executableby the controller to determine whether the reading performance hasimproved after adjustment, and in response to determining the readingperformance has improved, either: maintain the adjusted lateral readinglocation, or adjust the lateral reading location of the head in a samedirection and comparing a resulting reading performance with a previousreading performance.
 10. An apparatus as recited in claim 8, furthercomprising logic integrated with and/or executable by the controller to:determine whether the reading performance has improved after adjustment,and in response to determining the reading performance has not improvedadjusting the lateral reading location of the head by moving the headaway from the commanded lateral reading location in a differentdirection and comparing a resulting reading performance with a previousreading performance.
 11. An apparatus as recited in claim 8, wherein thedetermining, the adjusting, the comparing and the selecting areperformed continuously while the head is actively engaged in a readoperation.
 12. An apparatus as recited in claim 8, wherein the one ormore metrics are selected from a group consisting of C1 error correctionrate, and C2 error correction rate.
 13. An apparatus as recited in claim8, wherein the reading performance is determined using information frommultiple read channels configured to operate simultaneously.
 14. Anapparatus as recited in claim 8, further comprising: the head, whereinthe head is electrically coupled to the controller; an actuatormechanism for actuating the head in an analog domain; and a drivemechanism for passing a magnetic medium over the head.
 15. A computerprogram product, the computer program product comprising a computerreadable storage medium having program instructions embodied therewith,the program instructions readable and/or executable by a controller tocause the controller to: determine, by the controller, a readingperformance of a head positioned at a commanded lateral reading locationbased on one or more metrics; adjust, by the controller, a lateralreading location of the head relative to a medium by instructing thehead to move in a lateral direction away from the commanded lateralreading location to an adjusted lateral reading location; determine, bythe controller, a reading performance of the head after the adjusting;compare, by the controller, the reading performance after the adjustingto the reading performance before the adjusting for determining whetherthe reading performance has improved; and select, by the controller, anoptimal lateral reading location based on the comparing, wherein the oneor more metrics comprise one or more benchmark values captured duringone or more write operations.
 16. The computer program product of claim15, wherein the one or more benchmark values are selected from the groupconsisting of C1 corrections and C1 uncorrectable.
 17. The computerprogram product of claim 15, further comprising program instructionsreadable and/or executable by the controller to cause the controller todetermine whether the reading performance has improved after theadjusting, and in response to determining the reading performance hasnot improved, at least one of: instruct the head to restore thecommanded lateral reading location; instruct the head to maintain theadjusted lateral reading location, and instruct the head to adjust thelateral reading location of the head by moving the head away from thecommanded lateral reading location in in a different lateral directionand comparing a resulting reading performance with a previous readingperformance.
 18. The computer program product of claim 15, wherein theadjusted lateral reading location corresponds to a new lateral servolocation relative to a previous lateral servo location used prior to theadjusting, and wherein the new lateral servo location and the previouslateral servo location are spatially separated by a predefinedadjustment increment in an analog domain.
 19. The computer programproduct of claim 18, further comprising program instructions readableand/or executable by the controller to cause the controller to determinewhether the reading performance has improved after the adjusting, and inresponse to determining the reading performance has not improved, atleast one of: instruct the head to restore the commanded lateral readinglocation; instruct the head to maintain the adjusted lateral readinglocation, and instruct the head to adjust the lateral reading locationof the head by moving the head away from the commanded lateral readinglocation in in a different lateral direction and comparing a resultingreading performance with a previous reading performance; and in responseto determining the reading performance has not improved, at least oneof: maintaining the adjusted lateral reading location, and adjusting theadjusted lateral reading location by moving the head away from theadjusted lateral reading location in the lateral direction and comparinga resulting reading performance with a previous reading performancewherein the one or more metrics comprise a C1 error correction rate;wherein the one or more benchmark values are selected from the groupconsisting of C1 corrections and C1 uncorrectable, wherein the readingperformance is determined using information from multiple read channelsconfigured to operate simultaneously wherein the determining, theadjusting, and the comparing are performed continuously while the headis actively engaged in a read operation.